This invention relates generally to disc brake pads, and particularly to disc brake pads which are provided with a shim plate.
In a brake assembly, such as a disc brake assembly, a rotatable disc or rotor rotates with a wheel to be braked. Braking subassemblies, including brake pads, have a steel backing plate and a braking pad, and are disposed on opposite sides of the disc. As the subassemblies move inwardly under the force supplied by an actuated piston and a related caliper, inner surfaces of the braking pads are engaged in frictional, braking contact with the rotor. A high pitched and undesired squeal noise is often produced by vibration of the subassemblies during braking.
To reduce or to eliminate the undesired brake squeal noise, sound (or noise) dampening members, commonly referred to as shims, have been used by both original equipment manufacturers and by brake repair shops. Initially, only adhesives were used to attach the shim plate to the backing plate. However, one problem with the use of adhesives is they are subject to failure under very heavy duty use where the brake pad can reach extremely high temperatures. Consequently, the shim is liable to slip relative to the pad, and in some cases has been known to fall out of the caliper or cause damage.
Several embodiments exist in the art that are designed to further reduce shifting of the shim during braking. For example, a previous brake pad assembly provides for a disc brake pad and shim assembly including a backing plate and friction material on the opposite side of the backing plate. The backing plate has at least one recess through which projections of the shim plate extend to hold the shim plate in place.
In another prior brake pad assembly, the backing plate has incompletely filled spigot holes, and a shim has protrusions extending into the unfilled region of the spigot holes. This configuration prevents slippage of the shim across the backing plate.
In yet another brake pad assembly, rivet-like projections on the backing plate engage openings in the shim plate. The projections are then deformed once the shim plate is in place to hold the shim plate to the backing plate.